Cooling of iron mercury rectifiers



May 16, 1933. w HULL 1,909,105

COOLING OF IRON MERCURY RECTIFIERS Filed Aug. 1, 1930 Inventor: Albert W. Hull,

His Attorney Patented May 16, 1933 UNITED STATES PATENT OFFICE ALBERT W. HULL, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENIERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK COOLING OF IRON MERCURY RECTIFIERS Application filed August 1, 1930. Serial No. 472,322.

My invention relates to apparatus for transmitting power between alternating and direct current circuits thru a space discharge device such as a high capacity mercury arc irectifier. and its principal object is the provision of an improved structure whereby the occurrence of arc-back is minimized.

In the operation of high power mercury arc rectifiers, difficulty is frequently encountered due to arc-backs or short circuits between anodes of the separate phases.

One of the causes of arc-back is the dropping, upon an anode, oi mercury formed by the condensation of mercury vapor on the walls of the anode housing or seal or by the condensation of the vapor directly on the anode, the'mercury being'subsequently ionized bythe intense heat of the anode. In order to prevent arc-back from this cause,

it'has been suggested heretofore to provide electric or other special means to heat the anodesand anode housings or sleeves.

In accordance with my invention difliculty due to arc-back producedby the condensa- -tion of mercury vapor is avoided by the provision of temperature regulating means comprising. a bodyof water or other suitable heat absorbing medium which surrounds the anode housings and seals and the level of 39 which is maintained substantially at the level of the uppermost portion of the anode vacuum chambers.

My invention will be better understood from the following description when considered in connection with the accompanyingdrawing and its scope will be pointed out :in the appended claims.

Referring to the drawing, Fig. 1 is a cross-sectional view of a mercury arc recti- "fier. embodying my invention and Fig. 2 illustrates a modification of the anode seal.

The mercury arc device shown in Fig. 1 comprises a rectifier tank 10, a mercury cathode 11 and a plurality of anodes 12 of which only one appears in the drawing. Each one of the anodes is supported within an anode housing 13 projecting from the upper wall of the tank and having a sleeve portion. projectingv downwardly within the "tank. The supportingmeans for the anode comprises a seal which is mounted above the anode on the anode sleeve 13 and which insulates the anode therefrom. In order to maintain the operating parts of the rectifier at the required temperature during. idle periods and during periods of load, a water jacket 15 is provided which surrounds the tank and the anode housings and which is of such height that the water level may be maintained at the level of the uppermost portions of the anode vacuum chambers formed by the housing and seal, and preferably above the top of the seal 14. A jacket member 16 having. holes 17 therein for the flow of water is arranged to enclose the housing and seal. Since the water within sleeve 16 is substantially stagnant, the temperature of this water rises during operation above that of the surrounding water in jacket 15.

The anode seal 14 comprises a plate 18 secured to the upper end of anode housing 13, a terminal member 19, and an insulated and sealing member 20 of vitreous material attached to and separating the terminal member and plate. The anode 12 is secured in proper position within housing 13 and supplied with current from terminal member 19 by means of an anode stem 21 passing thru the insulating and sealing member 20 and connected to the terminal member, on which is mounted a terminal lug 22 for connection of the anode to a current supply lead. The insulating and sealing member 20 is surrounded by acontainer or sleeve member 23 containing oil, air, or other suitable medium and so arranged that any portion of the seal 14 projecting above the water level is protected from loss of heat which wouldotherwise occur due to radiation to the atmosphere. Auxiliary heating means such as an electric heating co il 241 surrounding anode housing 13 may be provided if desired.

In the seal illustrated in Fig. 2 the plate 18 supports a sleeve 25 rigidly secured thereto. A. stud 26 to which is connected an anode stem 27 is insulated from the sleeve 25 by a sealing member 28 of vacuum tight material such as micalex in contact with a sleeve 29 mounted on stud 26. When the structure shown in Fig. 2 is used in the rectifier shown in Fig. 1, the level of the cooling water in jackets 15 and 16 is approximately that of the lower end of the anode support comprising the sealing member 28.

In the system shown in Fig. 1, loss of heat from the anode 12 to the cooling water in the jackets occurs only by radiation to the water cooled housing 13 and by conduction thru the seal 14 to this housing. The temperature of anode 12 and seal 14 will, therefore, never fall below that of the housing 13. The water in the upper part of jacket 15 is always warmer than the water in the lower part of the jacket. Further, the water in jacket sleeve 16, surrounding the seal and the portion of the anode housing adjacent the anode, is still warmer than the water in the upper part of jacket 15. But the cooler water in the lower part of the jacket 15 determines the vapor pressure of the'mercury in the tank. Therefore, any condensation of the mercury vapor which takes place will be confined to the region extending from the anode downward, since condensation, at the vapor pressure determined by the cooler Water in the lower portion of the jacket 15, cannot take place on those surfaces which are surrounded by the warmer water in jacket sleeve 16, and which are themselves as warm as or warmer than the water.

When operation of the rectifier is interrupted the temperature of the water in chamber 16 will still remain above that in chamber 15 as the latter cools, provided loss of heat by radiation and conduction from terminal member 19 and adjacent parts is prevented by means of a suitable medium in sleeve 23, as heretofore described. When the temperature of the water in chamber 15 rises, due to resumed operation or any other cause, it is desirable that the temperature of the water in jacket 16 shall rise at an equal ,or greater rate. This may be assured by proper construction and dimensioning of chamber 16, including proper location and size of holes 17 to allow a slow circulation of water between jackets 15 and 16.

Complete protection against arc-back due to condensation of mercury vapor is assured when the cooling water in jacket 15 at the level of the upper end of the anode housing is maintained at a temperature slightlv above .that in the lower part of jacket 15. For example. if the temperature in the lower part of jacket 15 is 40 C., then a temperature of approximately 50 C. is sufiicient in the upper part of jacket 15.

It will be seen that, in accordance with my invention, arc-back due to condensation of the mercury vapor on the anode or in the vicinity thereof is prevented, and the use of special heating means for the anodes and associated parts may be obviated, by maintaining the level of the cooling water in the rectifier tank jacket at the level of the u per ends of the anode chamber, preferably a ove the upper ends of the anode seals, and thereby utilizing the difierences in temperature at the upper and lower levels of the cooling water, and by the provision of a bod of substantially stagnant water surroun ing the anode housing and the seal. It will be seen further, that these results are obtained without raising the temperature of the jacket water as a whole. On the contrary, the jacket water surrounding the tank is maintained at any desired temperature sufiiciently low to insure eificient cooling of the rectifier under load conditions.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a mercury arc device, the combination of an evacuated tank, an anode housing arranged to extend upwardly from said tank, means comprising a sealing member mounted above said anode to support said anode in said housing, means includin a jacket to surround said tank by a coollng medium, and means including a second jacket enclosing said housing to surround the housing by a substantially stagnant portion of the cooling medium in the upper portion only of said first-named jacket, the level of said medium being maintained above the lower end of said member.

2. The combination in a, mercury are device of an evacuated tank, cooling means for said device comprising a jacket arranged to surround said tank and acooling medium in said jacket, a second jacket arranged in the upper portion only of the medium in said first-named jacket and containing a substantially stagnant portion of said upper portion of the cooling medium, an anode, an anode housing projecting upwardly from said tank and surrounded by the medium in said second-named jacket, means to support said anode in said housing, said jackets being of sufiicient height to maintain the level of said medium above the lower end of said supporting means.

3. The combination in a mercury are device of an evacuated tank, cooling means for said device comprising a jacket arranged to surround said tank and a cooling medium in said jacket, an anode, an anode housing arranged to be surrounded by the medium in the upper portion of said jacket, means comprising a sealing member mounted above said anode to support said anode in said housing, said jacket being of sufiicient height to maintain the level of said medium above the lower end of said sealing member, and means associated with the portion of said member above the level of said medium to reduce the radiation of heat from said member.

4. The combination in a mercury are device of an evacuated tank, cooling means for said device comprising a jacket arranged to surround said tank and a cooling medium in said acket, an anode, an anode housing, means to support said anode in said housing, said jacket being of suflicient height to maintain the level of said medium above said housing, and means including a second jacket having walls the outside surfaces of which are in contact with the cooling medium in the upper portion only of said first-named jacket to surround said housing by a substantially stagnant portion of said cooling medium.

5. The combination in a mercury are device of an evacuated tank, cooling means for said device comprising a jacket arranged to surround said tank and a cooling medium in said jacket, an anode, an anode housing, means comprising a sealing member mounted above said anode to support said anode in said housing, said jacket being of suflicient height to maintain the level of said medium above the lower end of said sealing member, means comprising a jacket member surrounding said housing and said sealing member to maintain a portion of said medium substantially stagnant, and means associated with the portion of said member above the level of said medium to reduce the radiation of heat from said member.

6. The combination in a mercury are device of an evacuated tank, cooling means for said device including a jacket surrounding said tank and a cooling medium in said jacket, an anode, an anode housing projecting upwardly from said tank, said jacket being of sufficient height to maintain the level of said medium above said housing, and means including a second jacket having Walls in contact with said medium in said first-named jacket to surround said housing by a substantially stagnant portion of said cooling medium, said walls having openings formed therein for the slow circulation of said cooling medium between said jackets.

7 In a mercury arc device, the combination of an evacuated tank, an anode, an anode housing extending upwardly from said tank, means to support said anode in said housing, means including a jacket to surround said tank by a cooling medium, means including a second jacket immersed in the upper portion only of the medium in said first-named jacket to surround said housing with a substantially stagnant portion of the medium in said upper portion of the first-named jacket, the level of said medium being maintained above the lower end of said supporting means, whereby loss of heat from said anode by radiation to said cooling medium occurs only to that portion of said medium in said first named jacket which surrounds said upwardly extending housing.

8. The combination in a mercury are device of an evacuated tank, cooling means for said device comprising a jacket surrounding said tank and a cooling medium in said jacket, an anode, an anode housing sur rounded by relatively warm medium in the upper portion of said jacket, and means comprising a sealing member mounted above said anode to support said anode in said housing, said acket being of sufficient height to maintain the level of said medium above the lower end of said anode supporting means, said anode being mounted in said housing above the point at which said housing is joined to said tank to cause substantially all the heat radiated from said anode to said medium to be absorbed by the rela tively warm upper portion of said medium surrounding said upwardly extending housmg.

In witness whereof, I have hereunto set my hand this 31st day of July 1930.

ALBERT W. HULL. 

